Coupling system for wave guides



June 21, 1949. K. A. YQUNG 2,474,137

` COUPLING' SYSTEM FOR WAVE GUIDES Filed Feb. 15, 1944 z sheets-sheet 1 muws/Ty Hur 5//1/050/0 June 21, 1949. K. A. YOUNG COUPLING SYSTEM FOR' WAVEGUIDES Filed Fem 15, i944 2 Sheets-Shee' 2 'lll/lillIIllllllllllllllIlIIIlIlll/Illl 5f ML Patented June 21, 1949 UNITED STATES PATENT OFFICE GOIJPLINGSYS'EEM FOR WAVE GUIDES Kenneth A, Young, Waban, Mass., assigner to Raytheon Manufacturing Company, Newton,

Mass., a corporation of Delaware Application February 15, 1944SeralNQ. 522,481

12 Claims. 1v

This invention relates 5to. guidedelectromagneticwave transmissonsystems, and more particularly to, va transition ,d evicefor coupling a coaxial conductor transmission lineand a hol- W Wave, guide.

In coupling a coaxial line to aldielectric wave guide, it is desirable to` convert Athevvave form from one most suitableior propagation in the coaxial line to a form .suitable,for the geometry of thedielectric Wave guide, Whatever its con.- figuration maybe, Conversely v avvave passing throughthe system inzthe reverse direction should be. converted from thev type most desirablev for tranSmSsion throughthe guide toatype suitable for transmission in the .coaxial line.

It is among the ,objectsl oi theinventicn. to provdea device by Whichelectrornagnetic Wai/cs of one type, under propagation-in a guided Wave transmission system, may beV modified or reshaped so that after conversion they will be propagated as Waves vof a predetermined type.

In coupling the coaxial line yand a hollow Wave guide, it is generallyessential that the concentric line be joined to the wave guide in. avpredetermined direction. For examplefin coupling a concentric line to a rectangular wave. guide, it has heretofore been generally necessary to couple to the hollow Wave guide at some-predetermined position on the Wide dimension of the guide. If for structural reasons inherent in the transmission system the concentric line must approach the hollow Wave guide from adifferent side, such for example as from the narrow side thereof, then a Series .of transmission line sections dis.- posed at proper angles must be .introduced in the system in order that the concentric line may enter the Wave guide from the proper direction. Not only is the additional bulkand weight due to such bends or angles-objectionable, butthey also introduce additional mechanical complications in a system Where it is desired to rotate one section of the transmission line relative -to another, as in the case where the direction of propagation from an antenna system is to be varied. Furthermore, such bends necessarily vincreasethe electrical losses in thesystem.

It is a further objectl of the invention to provide a device of thetype described in the foregoing for effecting the desired transition between the concentric line and the hollow Wave Yguide in a simple direct manner without the introduction of complex bends or angles into the concentricline as it approaches the guide.

A further-object of the invention is to provide a device of the type described Whichuis suitable 2 for the transmission yof Waves of relatively high energy.

The invention Will be described as a transition dcricc from thc .priucipalwavc iu a coaxialtranc.- miSSon lille th@ L1 modelo a hollow 'cylindrioal Wave guide, and to the TE 0, lvmodfe in a rectangular cuido7 `.lult Shoulduot to collattilod as lilllltcd. to aus' particular mollo Also it Willbe uudcrctood that lthc .icycatiou may bcutllz'ed. lo transrlussion liucsv of lccscolumou Shares..-

Tec Aforegoing 'and other objects of tlloillvcetion will. lucy best. understood. from thc following detailed dcscrictlcc?. r'cfcrcucc todos hadto tlc? accompanying drawillg wherein? Fig. 1 is av section through one forni otrny novel trauattico dol/icc;

Flc.- 2 `is a .Scctiou tatou oc tho .lloc 2,-?of Fis. 1;

Fia 3 is a ydiastatllrluatic. vict? illustrating ,the mode of operation of the form of the invention shown in Figs. 1 and 2;

Fig. 4 is a section through another embodiment of the invention and istaken lon the line 4-4 of Fie. 6:

Fig., 5 is a Section .taken thc liuc V5-15.. .of Fis.v 4.:

Fig- 6 is .a .plan rlcw. of the form .of .the invoer tion .Shcwolu Figs. 4 aud;

Fig. 7 diagrammatically illustrates the mode of operation ,of .the ,form of, thc ,intention shown in Figs. 4, 5 and @and Fris. '7a` Shows dlas.ramutatica,llyv they eld `.distrbutton corresponding toria. '7.

Referring to the drawings, and rst to Figs.. 1:13 thereof, thejransition device in thisk instance includes a coaxial conductor transmission lillc-..l and a ,cylindrical waveV guido. ,2- Thccoaldallnc l comprises an outer tubular conductor Sand an innerconductor ,4 which is positioned centrally in the outer Vconductor excelztt at the endthereof where theconductorvis bent toucontact the, onductor 3 to the inner surfaceof which ltheconductor dis soldered `or,otherwise secured .tol p r o, vide good electrical connection therewith.

The coaxial line l, projects into the Wavet guide 2 at the approximate electrical center thereof. In this instance the wave guide is cylindrical and the coaxial line l projects into the Wave guide 2 iu., suclc. mauncr that thc-electrical ccntcrcf .tho radiating elementsliereaiter described extends into the round Wave guide for a distance approximately equal to one-quarter of the length of the waves which the system is adapted to transmit. 'Ihc cuter conductor is provided ara-lr, of diametrically opposed yslots 45y which entend from the end thereof within the wave guide 2 for a distance approximately equal to one-quarter of the length of the waves on the transmission line. Since a substantial portion of the walls of the tube 3 are cut away in forming the slots 5, a pair oi opposed tongues 6 is provided by the remaining material of the tube 3, and it is to one of these tongues that the conductor A is secured to pro vide a good electrical connection between the outer tubular conductor 3 and the inner conductor 4. A reflecting plug 'I closes the end or" the wave guide 2 and is provided with a central opening through which the outer tubular conductor 3 extends.

Guided Wave transmission lines of the type described in the foregoing are usually designed to carry electromagnetic waves of approximately a predetermined wave length which may be represented by A. If the length of the slot 5, as indicated in Fig. 1, is made approximately equal to a circuit which is resonant at the predetermined wave length k is provided by the slots 57 which resonant circuit has points of high potential at the tip ends of the tongues 6. The slots 5 may be designated as one-quarter wave length slots and may be said to be excited at the frequency corresponding to the predetermined wave length A. Waves are propagated in both directions in the Wave guide 2, that in the direction of the reflecting plate 1 being reected so that it combines in proper phase with the wave traveling in the desired direction.

In order that the reflected waves combine in proper phase with the oppositely directed waves.

the distance between the reecting plate I and the electrical center of the radiating slots 5 should be The term electrical center means point, or small area, or small volume from which, viewed from a point several wave lengths away, the electromagnetic energy appears to emanate. However, since the portion of the coaxial line which projects into the wave guide 2 alters the electrical characteristics of the portion of the guide so traversed, the actual distance that the coaxial line I projects into the wave guide 2 in order that the reected and direct waves combine in proper phase diiers from the theoretical. It will therefore be understood that when referring to distances in terms of wave length herein, the apparent electrical distance is meant, not necessarily the linear distance.

In the operation of this form of invention, when the coaxial line is working in the principal mode, a potential diierence varying with time is impressed across each of the slots 5. These slots 5 are excited with points of high potential occurring at the ends of the tongues Ii. Since the depth of each slot is electrically equal to the distance between the points of high potential as taken along the slots is equal to A circuit is therefore provided by each slot which is resonant at the frequency corresponding to i,

where A is the length of the wave upon the line I. A wave is propagated in guide 2 in both directions from the points of high potential at the ends of the tongues E corresponding to the wave form shown in Fig. 3 in which the curved arrows indicate lines of electrical intensity. The wave propagated in the direction of the reflecting plates l is reflected back and combines in proper phase with the wavespropagated in the opposite direction.

The above described form of the invention functions eciently as a transition device at relatively high power. I have found that the limit of power-handling capacity is usually evidenced by the formation of corona at the ends of tongues 53. To avoid this difficulty and increase the powerhandling capacity and yet retain the advantages possessed by the form 0f the invention previously described, the coupling may be modied in the manner illustrated in Figs. 4 6.

In this form of the invention the coaxial conductor transmission line II has its outer tubular conductor I3 projecting transversely through a hollow wave guide I2. In this instance the hollow Wave guide I2 is rectangular in transverse section and the coaxial line II enters the wave guide through one of the narrower walls thereof and extends to the opposite Wall. Slots I5 in the outer conductor I3 extend longitudinally of the portion of said conductor enclosed within the wave guide I2, and the inner conductor l 4 of the coaxial line II is bent to contact the inner wall of the outer tubular conductor I3 at a point intermediate the length of the slots I5. The portions of the tubular conductor I3 remaining after the slots I5 have been cut therein provide two opposed conductive strips I6 to one of which the central conductor I4 is electrically connected. In this case the length of the slots I5 is made approximately equal to one-half of the length of the waves on the transmission line and it will be observed that a conductive path is provided between the two strips I 6 around each end of the slots I5 by the material of the tube I 3.

The operation of this form of the invention is similar to the operation of the form previously described except that the length of the slots I5 is made approximately equal to The points of high potential occur at the mid point of the length of the slots. The distance between the points of high potential as taken along the slots is equal to in either direction. When the coaxial line is working in the principal mode, the slots I5 are excited as in the previously described form. A circuit is provided in each direction by each of the slots I5 from one of the high potential points to the other, which circuits are resonant at the frequency corresponding to i. A wave is propagated in the guide I2 in both directions corresponding to the form shown in Fig. 7 where the lines indicate the distribution of electrical intensity. The reflecting plate I'I, which is used when propagation is desired only in one direction, is positioned so that the reflected waves combine in proper phase with the direct waves. The distribution of the electric iield in the rectangular guide is indicated in Fig. 7a in which the ordinates represent corresponding points along the long dimension of the wave guide, and the absaggiare? scissas representtheirelative intensity of the field.

.This formof distribution ,is recognized asthefmost favorable form for the rectangular guide. Inthis form of the invention wave forms of a higher order orrnodelmaybe obtained by changing the iformsshown need not necessarily be rformed in4 the manner shown by cuttingslots inthe outer `'conductorand connecting the innerconductor to one ofthe strips of materialof thefouterconductor remaining after the slotting operation.

For example, the tongues', of the form shown in -aFigs. 1 and 2, mayfbe formed of separate :strips oficonductive material-attached to the enclosed end of the outer conductor, the inner conductor being connected as before to one of said strips. shown in Figs. 3, 4 and 5 may be formed separately from the outer conductor i3 and connected thereto in any desired manner, as by soldering, to provide the pair of diametrically opposed strips.

There has been herein described two embodiments of the invention. Many other embodiments, within the scope of the appended claims, will be apparent to those skilled in the art from a consideration of the forms shown and the teachings herein.

What is claimed is:

l. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow wave guide, said outer conductor extending into said wave guide and having slots in the side walls thereof within said wave guide dividing a portion of said outer conductor into conductive strips, said inner conductor being connected to said outer conductor at one of said strips.

2. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow wave guide, said outer conductor extending into said wave guide and having opposed slots in the side walls thereof within said wave guide dividing a portion of said outer conductor into a pair of conductive strips, the length of said slots being substantially equal to one-quarter of the length of the waves on said transmission line.

3. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow wave guide,n said outer conductor extending into said wave guide and having slots in the side walls thereof within said wave guide dividing a portion of said outer conductor into conductive strips, the length of said slots being substantially equal to one-half of the length of the waves on said transmission line.

4. A coupling system vcomprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow cylindrical wave guide, said outer conductor extending into said wave guide at the approximate electrical center thereof and having a pair of diametrically opposed slots in the side walls thereof within said wave guide dividing a portion of said outer conductor into a pair of conductive strips, said inner conductor being connected to said outer conductor at one of said strips.

5. A coupling system comprising a coaxial conductor transmission line having an outer con- Similarly, the strips I6 of the form/20 l yductor surroundingfian! inner; conductor;- a ihollow wave guide, said iouter: conductor extending iinto IsaidrWavezzguide fand .having slots yin ,theside walls :thereof within said AWave guide dividing :aportionrofcsaid outerconductor into conductive strips, :said zinner conductorzbeing connected to :saidouterzconductor `atone of said strips,the length of` said-slotsbeing substantially equal to .oneequarter of `the length of the lwaves on said .transmission line.

GEA-coupling systemcomprising-a coaxial conductorvtransmission line having an outer .con-

ductor `surrounding .anzxinner conductor, a hollow waveguide, said outer `conducto-r. extending :into said waveguide and -havinggslots in .the side walls .thereofwithin said wave guide dividing a :portion offasaid-outer conductor into conductive strips;v said inner l.conductor being connected to p'saidv outer .conductor at one. offsaid strips, the

length of said slots being :substantially equalto onei-ahalfiofithellength of the waves on said transmission line.

7. A coupling system comprising a. coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow wave guide, said outer conductor extending into said wave guide and having a pair of diametrically opposed slots in the side walls thereof Within said wave guide dividing a portion of said outer conductor into a pair of conductive strips providing a circuit resonant to the frequency of the electromagnetic waves on said system, said wave guide having a closed and spaced from the high potential points of said resonant circuit at a distance substantially equal to one-quarter of the length of the Waves on said system.

8. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow rectangular wave guide, said outer conductor extending into said wave through the narrow side thereof, and having a pair of diametrically opposed slots in the side Walls thereof within said wave guide dividing a portion of said outer conductor into a pair of conductive strips.

9. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow rectangular Wave guide, said outer conductor extending into said wave guide through the narrow side thereof and having a pair of diametrically opposed slots in the side walls thereof within said wave guide dividing a portion of said outer conductor into a pair of conductive strips, said inner conductor being connected to said outer conductor at one of said strips.

10. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow wave guide, said outer conductor extending into said wave guide and having a pair of diametrically opposed slots in the side walls thereof within said Wave guide dividing a portion of said outer conductor into a pair 0f conductive strips connected together at each end by said outer conductor, said inner conductor being connected to said outer conductor at one of said strips.

11. A coupling system comprising a coaxial conductor transmission line having an outer conductor surrounding an inner conductor, a hollow wave guide, said outer conductor extending into said Wave guide and having a pair of diametrically opposed slots in the side walls thereof within said wave guide dividing a portion of said outer conductor into a pair of conductive strips,

said inner conductor being connected to said outer conductor at one of said strips.

12. A coupling system comprising a coaxial conductor transmission line having an outer conduotor surrounding an inner conductor, a hollow Wave guide, said outer Conductor having a portion projecting into said Wave guide, said portion of said outer conductor having an opening Within said Wave guide, the dimensions of said opening being correlated to the frequency of the 10 electromagnetic waves on said transmission line to form a circuit at said opening resonant to. said frequency, said central conductor being electrical- 1y connected to said outer conductor at a point within said portion of said outer conductor enclosed by said Wave guide, said Wave guide having a closed end spaced from the high potential points of said resonant circuit at a distance substantially equal to one-half of the length of the Waves on said system.

KENNETH A. YOUNG.

REFERENCES CITED The following referenlces are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,106,769 Southworth Feb. 1, 1938 2,232,179 King Feb. 18, 1941 2,250,096 Engbert July 22, 1941 2,253,503 Bowen Aug. 26, 1941 2,311,520 Clifford Feb. 16, 1943 2,317,503 Usselman Apr. 27, 1943 2,408,032 Beck Sept. 24, 1946 FOREIGN PATENTS Number Country Date 116,110 Australia Nov. 4, 1942 Certificate of Correction Patent N o. 2,474,137.

KENNETH A. YOUNG Y It is hereby certied that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 33, claim 7, for closed and read closed end; line 41, the Word Wave insert guide;

and that the said Letters Patent should be read With same may conform to the record of the case in the Patent Oce.

Signed and sealed this 22nd day of November, A. 13,1949.

claim 8, after THOMAS F. MURPHY,

Assistant Commissioner of Patents.

June 21, 1949. 

